Two techniques have been applied to exploratory well air drilling operations. These include air coring and operating the Dynadrill with air. The purpose is to maintain the ability to air drill below cored intervals and/or after making directional corrections or whipstock operations. Application of these techniques has allowed drilling the remaining footage of hole with air, at an increased penetration rate when compared with fluid, and thus reduce overall well cost. This paper presents the operating conditions and techniques used for air coring and operation of the Dynadrill based on actual well air and air-mist operations, are reviewed to established guidelines for equipment requirements and equipment performance.

The MSDU 1 (Mary Scharbauer Devonian Unit No. 1) was completed in December 1998. It was Mobil Drilling Midland's first attempt to drill a horizontal lateral while underbalanced. The Mary Scharbauer experience provided valuable data on the benefits and drawbacks of UBD (Underbalanced Drilling) in the extended reach environment. Increasing ROP in order to reduce cost was the primary goal of the MSDUl project. Increases in ROP from UBD were apparent when optimal bottom hole pressure was achieved. Maintaining optimal bottom hole pressure was impossible do to the limitations of conventional MWD (Measurement While Drilling) equipment. Extensive drill stem deterioration caused project costs to skyrocket and placed any future UBD projects on hold until a solution to the problem could be developed. Investigation of the drill stem corrosion showed that the most severe pitting occurred on the drill pipe in the lateral section of the well. Analysis of the drill fluid as well as formation fluids showed that the most reasonable explanation for the deep pitting observed on the drill pipe was "Oxygen Erosion Corrosion." Oxygen erosion corrosion was then simulated in the laboratory in an apparatus that produced conditions like those found in the lateral section of the MSDUl well. Many corrosion tests were completed in an effort to find inhibitors that would function in a deep, hot, oxygenated, and abrasive well bore environment like that of the MSDUl well. While this was being done 99.9+ % oxygen free UBD methods were evaluated. Eventually a corrosion inhibition system that worked under conditions like those of the MSDUl was located and proven on Mobil Midland's second UBD extended reach well the PFU 23-24 (Parks Field Unit 23-24). Conventional MWD equipment required that the drill pipe be loaded with water in order to generate a readable mud pulse. When surveys were needed underbalanced conditions were eliminated and ROP on the MSDUl dropped from 26ft/hr to 8ft/hr. Optimum underbalanced conditions were recovered after the well bore could be re-gasified. It was estimated that using a MWD system that did not require the drill pipe to be loaded would cut the cost of drilling a MSDUl like lateral by $60,000. Midland Drilling located an EM MWD (Electromagnetic Measurement While Drilling) company that stated their equipment would work for drilling a Devonian lateral underbalanced. When the equipment was evaluated on the PFU 23-24 it performed acceptably but learning were documented that will improve future operations. Mobil Drilling Midland continues to develop technology to improve bottom line profitability. Currently work is being done to determine the feasibility of drilling extended reach horizontal laterals with air compressors and a water/foam drilling fluid. If feasible this method will be half as expensive as our current lowest cost UBD option. The drilling curve will continually shift to the left as key learnings are implemented on fume projects.

Construction design and operating procedures for underground injection of brine waters are receiving more attention as the industry progresses toward full implementation of the provisions of the EPA Underground Injection Control regulations. Specific problems common to most injection well design and operation are discussed including casing and cementing programs, injectivity testing and reservoir performance calculations. Special emphasis is placed upon limiting surface injection pressures to avoid such hazards as invasion of potable water reservoirs.

This paper is presented as a reference for drilling. washing and completion of storage wells in the Salado Salt Section of the Eastern New Mexico-West Texas Area. The discussion and recommendations expressed herein are based on the experiences and problems encountered by the El Paso Natural Gas Products Company in its operation of the Odessa complex LPG storage wells.

Gas interference continues to be one of the major operating problems in pumping wells. In order to combat this problem effectively, we need a better understanding of what the pump volumetric efficiency should be under various well subsurface conditions Once we know how the pump should perform, it will be possible to select the best setting depth and determine whether a gas anchor is needed. Care must be used in the selection and in the installation of gas anchors, otherwise the results will be disappointing. If free gas is present, not only must an effective gas anchor be used but also must the pump develop a high compression ratio Thus, the type and design pump used is critical. Pumping wells from under a packer and small diameter casing completions are two practices that have increased the gas interference problem. Pump efficiencies and production can often be improved in such type wells.

As the cost of maintenance of gas transmission lines and plant maintenance at gas gathering sites has increased, the detection and control of 02, H2S, and CO, has become an important issue in cost controls and safety. Even though the actual costs related to the presence of these elements isn"t known exactly, the cost per location is estimated to be in the millions of dollars annually. The corrosion-related cost to the transmission pipeline industries is estimated to be between $5 billion and $8 billion annually. Obviously, all of these costs can"t be attributed to of 02, H2S, and CO,, but these three elements are a large contributing factor to these costs. In some gas high levels of CO, is present; therefore the removal of this element to meet the 4% contractual requirement is necessary thus contributing to the cost. In addition, CO, is an acid gas that contributes to the corrosion problem. The safety of transmission lines has a far-reaching affect including life, property damage, and large monetary liabilities for the transmission companies involved. Early detection and preventing the corrosion of these transmission lines, which in turn, prevents pipeline explosions, is extremely important. These elements accelerate the corrosion on all carbon steel components including the pipeline systems and components in plants. It is true that most of the carbon steel systems are protected with corrosion inhibitors, but large quantities of oxygen cause the inhibitors to have a limited amount of protection. It has been determined that oxygen levels of 10 PPM or less will have very little affect on these inhibitors. The identification of sources of oxygen and the recognition of hydrogen sulfide and carbon dioxide present in natural gas has become very important to corrosion prevention programs. The cost of this identification and elimination of the sources is far less than the cost of the repair and the liabilities of the corrosive affects if left unattended.

As CO2 miscible flooding becomes commonplace in our industry, more and more emphasis is given to gas dehydration and corrosion control in CO2 handling systems. This paper deals with the design of CO2/methane dehydration facilities, related metallurgical considerations, and the sizing of contact towers and reboilers to meet the varying CO2 concentration expectancies.

Artificial neural networks (ANN) are computer programs designed to mimic the functioning of the human brain. ANNs can be designed to "learn" by reviewing a data set consisting of a set of known inputs and a corresponding set of desired outputs. Once an ANN has been trained, it can predict outputs given just the set of known inputs. While the applications are broad reaching, one valuable application of such tools is in petroleum exploration. In places where both exploration data (such as log, core or geophysical data) and production data are available, a network can be designed and trained and used to predict production given a similar suite of exploration data. This work will discuss design issues in exploration neural networks, explore available software and review two case studies where neural networks were used to predict total production for undrilled sites in two formations in the Permian Basin.

Recent inflation has caused many in the industry to try and develop methods to improve the efficiency of their well repair programs. BP America, in cooperation with Key Energy, has begun a pilot program in SENM that couples existing KeyView data with a basic root cause perspective to deepen the understanding of service rig delays. This paper will discuss in general terms, the capability of the KeyView data capturing system, and in specific terms, how the available data was adapted to challenge assumptions about service rig delay times.

Gas lift is a flexible and forgiving form of artificial lift. Gas lift is so flexible that many installations for offshore platform wells are designed and the retrievable gas lift valve mandrels are installed during initial well completion. Efficient gas lift operations can be anticipated from installation designs based on limited well performance data by avoiding excessive distance between valve depths. The daily production rate from most gas lift installations depends upon the well deliverability and the available injection gas pressure and rate. The gas lift designs and systems described in this paper are not typical installations that are discussed in gas lift textbooks. The design concepts are not original and most of the information has been published in years past. The same innovative ideas reappear in cycles and will seem new to the engineer who has recently entered the petroleum industry. This paper brings together the description of several unusual gas lift applications into a single publication. Hopefully, one of these special installation designs will be a solution to a present artificial lift problem. Modification of an installation design tailored to a particular well or field is left to the reader.

It is the purpose of this paper to discuss several chamber gas lift installations in which the chamber operation produced more fluid than anticipated. Several unusual installations are reviewed.

Increasing wellbore complexity and increasing pressure to improve drilling economics has necessitated increased focus on preventing lost circulation. This has required a close focus on wellbore stability and improvements in wellbore strength such that losses are minimized or alternately casing strings may be eliminated. In addition the drilling of depleted zones in the same section as normally pressured formations has led to increased focus on maintaining wellbore integrity and minimizing losses. The development and engineering of unique drilling fluid additives which can aid in increasing wellbore stability and minimizing fluid losses into drilling induced fractures has been a key in achieving the desired operational goals. The Authors will discuss the design of these unique drilling fluid additives and the treatment techniques required to ensure optimal wellbore stability and minimal induced fracture losses, along with the engineering tricks required to ensure successful application of such treatments.

This paper presents two field case histories from multiyear horizontal completion projects in west Texas that were very successful at exposing the "false economy" of not cementing casing in horizontal wells drilled in low-permeability reservoirs. Moderate increases of 20 to 25% in initial well costs yielded a 3- to 10-fold increase in discounted cash flow through improved hydrocarbon recoveries. Case histories are developed for adjoining wells with similar reservoir characteristics and differing completion techniques. Comparisons of single lateral cemented liner completions to openhole completions and uncemented liner completions will also be presented.

Problems related to paraffin and asphaitenes continue to plague the oil and gas Industry. These include solid deposits, stabilization of emulsions and sludge production"'. Common solvents and condensates are popular treatments for dissolving and/or controlling paraffin and asphaltene related problems. Typically, these fluids have been used with little regard for long term effectiveness and formation damage consequences. Unique condensate feedstocks with high multiple aromatic content were identified. Laboratory testing, blending and refining resulted in solvents that can keep paraffin and asphaitenes in solution under a wide range of conditions. As a result of this work condensates are blended and refined to maximize solvency, demulsifying properties and maintain wettability without the addition of chemical additives. The properties of these refined natural solvents offer economical alternatives and/or enhancement to common treatment practices including hot oiling, condensate treatments, chemical treatments, stimulation and production treatments.

The Unit Operating Agreement is the contract among unit working interest owners which controls their respective functions in unitized operations. While the provisions of the operating agreement related to field wide units are generally acceptable to non-operators, there are, however, some areas of concern. The purpose of this paper is to briefly discuss some of those problem provisions.

Recognizing and cost effectively eliminating liquid loading in natural gas wells through the use of low pressure wellhead compression. The use of compression to eliminate liquid loading can be utilized in conjunction with other production methods such as soaping, siphon strings, plunger lift and beam pumping. Desireable features of low pressure natural gas compression will be highlighted with actual field cases illustrating the equipment characteristics needed for successful de-liquification of natural gas wells. Through computer analysis of pressure and area flow rate analysis, along with field testing and continued montitoring, the changing of compressor clearances, in conjunction with control valves, can be optimized to successfully keep gas wells unloaded during a longer period of time without resizing and replacing the compressor. Thus far the proper sizing and utilization of low pressure wellhead compression has enabled operators to maintain higher producing rates and velocities to keep gas wells unloaded which increases the monthly cash flow to the producer and extends the economic life of properties which leads to the recovery of increased incremental reserves.

The Variable Slippage Pump

More and more interest is generated for fiberglass tubulars because of their excellent corrosion resistance and mechanical strength. The major obstacle for more extensive use of fiberglass has been the lack of recognized engineering standards that would allow the field engineer to specify fiberglass with confidence for a particular application. Recognizing this need, several API committees are at work with unusual speed and efficiency to develop product specifications for fiberglass tubulars. Specifications for low-pressure line pipe were issued in 1986. Specifications for high-pressure line pipe followed in 1988. A specification for fiberglass downhole tubing is expected to be issued next year, in 1991. Finally, a specification for fiberglass casing is planned to be issued in 1992. This paper summarizes these API activities and details API fiberglass product specifications, both those issued and those still in committee.

More and more interest is generated for fiberglass tubulars because of their excellent corrosion resistance and mechanical strength. The major obstacle for more extensive use of fiberglass has been the lack of recognized engineering standards that would allow the field engineer to specify fiberglass with confidence for a particular application. Recognizing this need, several API committees are at work with unusual speed and efficiency to develop product specifications for fiberglass tubulars. Specifications for low pressure line pipe were issued in 1986. Specifications for high pressure line pipe followed in 1988. A specification for fiberglass downhole tubing is expected to be issued next year, in 1990. Finally, a specification for fiberglass casing is planned to be issued in 1991. This paper summarizes these API activities and details API fiberglass product specifications, both those issued and those still in committee.

ARC0 Oil and Gas Company has completed six drainhole wells in the Empire Abo Unit and plans to complete four more in early 1984. A drainhole well is one in which the wellbore has been deviated from vertical to horizontal with a turn radius of 20 to 30 ft. The horizontal hole extends up to 200 ft. Figure 1 illustrates an ideal drainhole completion. The increased surface area open to flow in the oil column reduces the susceptibility to gas coning as compared to conventionally completed wells. "Conventional Well" refers to a cased, vertical wellbore which has been perforated and acidized, (Fig. 2). A density-controlled acid job is generally used when stimulating to prevent etching upward to the gas cap. Even with the density-controlled method, significant upward etching occurs, increasing the susceptibility to gas coning. Initially, new wellbores were drilled for the drainhole completions. Recently a technique was devised and tested in the field to complete existing cased wellbores as drainhole wells. The main advantage of this new procedure is a substantial saving in drilling and completion costs. This paper summarizes the observed performance of the drainhole wells. A basic outline of the procedures used to drill the first six drainhole wells is included.

ARCO Oil and Gas Company started producing the nation's first large-scale natural carbon dioxide (C02) reservoir on January 31, 1983, from the Sheep Mountain Unit located in Huerfano County, Colorado. With the installation of a 330 MMCFD capacity pipeline, completed in January 1983, this CO2 has become an important source for future enhanced recovery projects in the West Texas area. This paper describes the Sheep Mountain reservoir, including a geological history, and the current theories for CO2 creation and migration in the Dakota and Entrada formations. A comparison of CO2 fluid properties to hydrocarbon fluid properties is presented, followed by a discussion of the producing characteristics of the wells and the conditioning processes employed before the CO2 is placed in the pipeline. An account of the problems encountered since start up and the resulting or proposed solutions is also included.

The purpose of this paper is to present an objective non-technical discussion, describing and comparing surface and downhole analysis. Previous discussions of surface and downhole analysis have been offered with only casual reference to each other. Both surface and downhole analysis can play an important role in practical well analysis programs.

A Pressure Vessel Management System (PVMS) using a computer program called PVCALC has been used extensively by Conoco's Midland Division for the last two years. PVMS was originally implemented (intra-Division) to be sure that all new pressure vessels bought for the Midland Division met the ASME Code. The program has been expanded to analyze surplus equipment. Vendor designs on at least 17 new pressure vessels have been analyzed, with only 12% of the vessels meeting ASME Code on first analysis. Ten surplus pressure vessels have been analyzed with PVMS and used, saving $500,000. The paper will cover the different problems that were found and actions taken to ensure that all pressure vessels meet ASME Code.

Recent field tests in South Louisiana have culminated a three-year research project by Baroid. The project objective was to apply the computer expertise developed while producing Baroid's CDC (Computerized Drilling Control) units introduced in 19711 to the development of an automatic pore pressure logging system. The CDC units require crews of up to seven people. The proposed system was to require only three crew members through more reliance on the computer for data collection, analysis, and presentation. The system (now designated Automatic Logging Service - ALS) evolved through several distinctive developmental phases. The first was the theoretical phase in which a mathematical model of the drilling operation was developed. This phase was reported by Bourgoyne and Young in 1973.2 The second phase consisted of field-testing the model through use of electronic calculators at the well site. The third phase was to implement the model in software for a mini-computer designed for real-time operation. The fourth and recently completed phase was to field-test the complete equipment and software package system. The ALS unit is designed to use a modern digital mini-computer, sensor devices, a system of mathematical equations, and one operator per tour to produce a pore pressure log on a continuous basis while drilling. Computer system responsibilities include data monitoring, storage, analysis, and presentation. Data collection is accomplished through the use of rig-mounted transducers that monitor the drilling parameters and transmit analog signals to conditioning panels. These panels then convert the transducer outputs into computer compatible signals. The computer reads and scales these values into engineering units. Parameters being automatically monitored are depth, hook load/bit weight, rotary speed, pump strokes per minute, on/off bottom, catalytic mud gas, and thermal mud gas. Parameters manually entered into the computer are mud density, shale density, sand/shale percent, and pertinent wellbore constants. Drilling data storage is accomplished through the use of a magnetic cassette tape unit that is fed from the computer on a time and event basis. Events that cause tape records to be generated are: the beginning of a bit run, the end of a bit run, the completion of a drilling interval, and the completion of a lag interval. During drilling, data averages are accumulated until an interval is completed. These averages are then stored on the tape. Records are created of certain data lag arrays on a time basis to minimize loss due to power failure. These lag arrays are dumped onto tape every 15 minutes. The system recovery program, following a power outage, automatically reads the most current lag array record into memory. The format of the stored data permits easy on-site utilization. Data analysis is done by applying the drilling model and drilling response equations. Drill rate is computed from the depth and on-bottom signals for several interval sizes (1, 2, 5, and 10 feet)

Paraffin problems can now be controlled economically by the use of a chemical dispersant. This paper reports on the progress made thus far with the use of a new chemical dispersant, available in four forms for field application ease; the location of certain major problem areas; and the various geographical locations where these new dispersants have been effectively used. Realizing one of the problems for making products of this nature work is precise field application; this paper also presents a scientific method for determining the treating requirements for two of the forms.